JPEG LI

What is JPEGli?

Jpegli is a new JPEG library introduced by Google this week. Its an advanced JPEG library which offers backward compatibility, an improved compression ratio of 35% and other enhanced capabilities.

The Jpegli encoder/decoder is fully interoperable with the original JPEG standard.

Key benefits of this new library include -

• Higher Perceptual Quality - With lesser artifacts than the original JPEG, images encoded with Jpegli will have a higher visual quality.
• Fast Encodes/Decodes - Jpegli has encode speeds similar to the other JPEG enhancements/libraries - libjpeg-turbo and MozJPEG. (will write on these libraries in a later blog).
• 10-bit or more - Jpegli supports a higher color depth compared to the original JPEG standard which was limited to a maximum of 8 bits/pixel. The 10+ bit encodes happen in the original 8-bit formalism thus the resulting images are fully interoperable with 8-bit viewers.

So how is Jpegli able to improve over the original JPEG standard by such significant margins?

Well the secret sauce is it’s inspiration from JPEG-XL. One of the primary techniques is adaptive quantization heuristics which it largely borrows from the JPEG-XL reference implementation. Jpegli combines this with a few other enhancements while remaining fully compatible with the existing JPEG viewers - browsers, software etc.

Source : Google. A higher ELO score indicates a better aggregate performance in the rater study. We can observe that jpegli at 2.8 BPP received a higher ELO rating than libjpeg-turbo at 3.7 BPP, a bitrate 32 % higher than Jpegli.

Google has open-sourced this library, you can download here - https://github.com/libjxl/libjxl/tree/main/lib/jpegli

I intend to run a few tests with Jpegli and share the results and more in a later blog.